Engine starter



Patented May 18, 1943 James E. Buxton, Ehnra, N. Y., assigner to Bendix Aviation Corporation, South Bend; Ind-r,

a` corporation of Delaware Application January 2s, 1942, serial No.Y 427,959

3 Claims. (Cl. 74-7) The present invention relates' to an engine starter and' more particularly to automatically engaging' starter gearing incorporating a yielding driving element of elastically deformable material.

lIn those starter drives' utilizingV elasticall'y deformable materialsuch as'r'ubber which is placed' under compression during the operation' of the drive it has been found that if', in such operation, the yielding member is compressed' until it' llsthe' entire space which it occupies, itsyielding 'function is substantially'lost, and' the drive acts as though it were a solid mechanical connection'. 'This is caused bythe' fact that the rubber itself is 'substantially' incompressible, j ust' as wa'- ter, for'instance, isincompres'sible, and ist evid'enced' by aharsh thumpingnoise caused' by the imposition of shock loads on the partsV of1 the drive. Moreover, if Vthe elastically deformable material is subjected to peak torque loads at the'time' that it is compressed solid, the engaging surfaces thereof are scrubbed and abraded so as to cause comparatively rapid deterioration of the yielding element.

It is an object of the present invention to provide a novel engine starter drive incorporating a yielding member of elastically deformable material which is arranged to limit the compression of said material to a point where it does not completely fill the space it occupies.

It is another object to provide such a device in which peak torque loads are taken by an auxiliary driving connection brought into operation by the compression of the elastically deformable material.

It is another object to provide such a device in which the means for limiting the compression of the elastically deformable material constitutes the auxiliary torque-transmitting means.

Further objects and advantages will be apparent from the following description taken in connection with the accompanying drawing, in which:

Fig. 1 is a side elevation partly broken away and in section of a preferred embodiment of the invention showing the parts in normal or idle position, and;

Fig. 2 is a similar view showing the parts in cranking position.

In Fig. 1 of the drawing there is illustrated a y power shaft I which may be the extended armature shaft of a starting motor not illustrated. A pinion 2 is slidably journalled on the power shaft for movement i-nto and out of engagement with a member'such asa gear 3 of anengine'tobe started, the`- operative position or the pinion' being: de'-A iined by' a thrust collar 4, seated' againsta shoulder 5 on the p'owerjs'haft.

A' screw shaft 6' is rfixed onthe power shaft-as by means of a driving pin T `and `has threaded thereon a nut 8 having a 'radial flange 9 and a sn'ioothjv cylindrical' extension It. The nut 8 is preferably counter-bored as indicated at l2A soas to enable the nutl to run oif the ends of the threads of the screw shaft; and` the nut is' riorrnally maintained: inidleposition by meansof an antild'rif't pin I3" which cooperates'0 with an inclined shou1dfe1f Non the screw shaft by means of a springU ring I5' seated in aj groove of the nut and pressing' the pin againstthe'shaft.

A ra-entry spring i6 is; arranged to press the nut in a direction to` engageit'sthreads"with the threads of the screw shaft, theexpansiori'of said s'pri'ng being limited by engagement of a tliimble IT with" a flange" f8 on tliefs'crew'shaft.

Pin'iorf112has`a barrel lllfixed" tneeon'ir an? suitable manner' as indicated atl 2l'. Barrel I9 has a radial flange 22 similar to the flange 9 of nut 8, and is further provided with a cylindrical portion 23 adapted to have a loose bearing t on the cylindrical portion Il of thenut 8 so as to permit relative rotation and telescopic movement of the nut and barrel.

A cylindrical block 24 of elastically deformable material such as rubber is located between the flanges 9 and 22 0f nut 8 and barrel I9 respectively, and is maintained in frictional engagement with said flanges by means of a sleeve 25 surrounding said flanges and spun over at its ends as indicated at 26 and 2l, so as to limit the separation of the flanges. The chamber formed by the nut 8, flanges 9 and 22 and sleeve 25 is larger in volume than the elastic block 24, so that considerable endwise compression of the block may take place before the block will ll said chamber. According to the present invention means are provided for limiting the telescoping movement of the nut and barrel so as to prevent the elastic block from being compressed solid within its chamber. As here shown, this means is in the form of a clutch ring 28 of a suitable material such as fiber, seated in the barrel I9 in position to engage the end of the nut 8 and limit the telescoping movement of the nut and barrel as shown in Fig. 2. At the same time this clutch member is arranged to frictionally transmit torque directly from the driving member constituted by the nut 8 to the driven member consti-tuted by the barrel i9, so as to relieve the elastio block from peak torque loads.

In the operation of the device, starting with the parts in the positions illustrated in Fig. 1, rotation of the power shaft l causes the screw shaft 6 fixed thereon to rotate and thereby traverse the nut 8 to the right, which traversal is transmitted through the elastic block 24 to the barrel I9 and pinion 2 to cause the pinion to mesh with the engine gear 3 until its longitudinal movement is arrested by the thrust ring 4. Further movement of the nut causes the elastic block 24 to be compressed between the driving ange 9 and driven ange 22, and at the s-ame time torque is transmitted through the elastic frictional connection so formed. After a predetermined amount of such compression has taken place, the end of the nut 8 engages the clutch member 28 in the barrel, thus preventing further compression of the elastic block, and establishing an auxiliary frictional driving connection directly between the nut and barrel. This auxiliary connection is in effect a self-tightening friction clutch which transmits without shock the peak torque loads and prevents overloading of the elastic element 24.

When the engine starts, the overrunning of the engine gear causes the parts to be returned to their idle positions where they are maintained by means of the anti-drift pin I3. Y

Although but vone embodiment of the invention has been shown and described in detail, it will be understood that other embodiments are possible and various changes may be made in the design and arrangement of the parts without departing from the spirit of the invention as defined in the claims appended hereto,

What is claimed is:

1. In an engine starter drive a power shaft, a pinion slidably journalled thereon, a stop on the power shaft defining the operative position of the pinion, a screw shaft xed to the power shaft,

a ai'ged barrel member fixed to the pinion, a anged nut member on the screw shaft in telescopic relation with the barrel, a block of elastically deformable material interposed between the flanges of the barrel and nut and in frictional engagement therewith, and clutch means in the barrel limiting the telescopic movement of the nut into the barrel and forming an auxiliary friotional connection therebetween.

2. In an engine starter drive a power shaft, a pinion slidably journalled thereon, a stop on the power shaft dening the operative position of the pinion, a screw shaft xed to the power shaft, a flanged barrel member xed to the pinion, a flanged nut member on the screw shaft in telescopic relation with the barrel, a block of elastically deformable material interposed between the flanges of the barrel and nut and in frictional engagement therewith, and frictional clutch means in the barrel engageable by the end of the nut to limit the entry of the nut into the barrel and thereafter forming a friotional torque-transmitting connection between the nut and the barrel.

3. In an engine starter drive a power shaft, a pinion slidably journalled thereon for movement into and out of engagement with a member of an engine to be started, and a yielding driving connection between the shaft and pinion including driving and driven members, a block of elastically deformable material interposed therebetween, and torque-responsive means for compressing the block between said members, means cooperating with the driving and driven members to form a chamber for the block of elastically deformable material and means for stopping the compression of said block before it lls said chamber, said stopping means also forming a direct clutchv connection between the driving and driven members.

JAMES E. BUXTON. 

